The Research Of T-foil&Flap’s Effect On Wave-piercing Catamaran Seakeeping

Wave Piercing Catamaran (WPC) is a new high performance vessel, which appeared morethan40years.WPC has more wide deck area than single hull, which can carry more goodsand tourists, and its speed can be as high as40-50kn. In bad sea condition, the vessel in highspeed can shake badly, which has a negative impact on the crew and cargo security. How toimprove the seakeeping performance in the bad sea conditions is significant for passengercomfort, vessel safety and performance exploited.The WPC longitudinal motion is studied in this paper, and the STF strip theory is used forseakeeping prediction. T-foil and flap is used to improve seakeeping.T-foil has emerged in the last20years, flap for half a century. T-foil is usually installed inthe precursor, improving the most violent motion. Flap mounted at the tail, not only improvethe seakeeping, but also play a role in reducing resistance.T-foil is influenced by free surface, about which theories and experiments can be seen a lot.However, no theory about flap can be found, only some experiments found. The flap’shydrodynamic performance is complex. Considering free surface, T–foil lift formula is derived.Considering the coupling of transom stern, free surface and rooster tail, lift coefficient slopeand zero lift angle about flap is derived. The formulas derived and experimental results are ingood agreement. The formulas are used to deal with the wing part of WPCseakeeping. The separate function and the two coupling on WPC seakeeping are studied, whichis helpful for fine seakeeping analysis.For the WPC seakeeping calculation, the hydrodynamic coefficients is solved by potentialflow theory, the STF strip theory is used to forecast WPC seakeeping. For ship with T-foil andflap seakeeping prediction, steady wing theory is mostly used to deal with T-foil and flapcurrently, but the peak prediction error grows largely. In order to improve the WPC seakeepingprediction, vibration wing theory is firstly applied to hydrofoil in WPC seakeeping prediction.The anti-pitch mechanism of T-foil and flap is described, peak forecast error is reduced. Theintroduction of vibration wings, not only can improve the accuracy of seakeeping prediction, butalso can optimize hydrofoil for seakeeping in future.